How do I decode a Base64 string online?

Paste your Base64 string into SmartDevBox at smartdevbox.com. It automatically detects Base64 encoding and decodes it instantly — no configuration needed.

How do I decode a JWT token without a secret?

Paste your JWT token into SmartDevBox. The JWT Inspector tool decodes the header and payload and displays them as readable JSON. Note: this decodes but does not verify the signature — you don't need the secret to read the claims.

How do I format or pretty-print JSON?

Paste your minified or unformatted JSON into SmartDevBox. The JSON Formatter tool detects it automatically and pretty-prints it with configurable indentation.

How do I convert a Unix timestamp to a human-readable date?

Paste a Unix timestamp (e.g. 1700000000) into SmartDevBox. The Unix Timestamp converter detects it and shows the equivalent date and time in UTC and your local timezone.

How do I convert JSON to CSV?

Paste a JSON array of objects into SmartDevBox and select the JSON → CSV tool. It converts your data to comma-separated format with headers derived from the JSON keys.

How do I compute a SHA-256 hash online?

Use the Hash Generator tool on SmartDevBox. Paste any text and it computes MD5, SHA-1, SHA-256, and SHA-512 hashes simultaneously in the browser.

How do I parse and understand a cron expression?

Paste your cron expression (e.g. "0 9 * * 1-5") into SmartDevBox. The Cron Job Parser explains it in plain English and shows the next scheduled run times.

How do I decode an X.509 certificate online?

Paste a PEM-encoded certificate (beginning with -----BEGIN CERTIFICATE-----) into SmartDevBox. The Certificate Decoder extracts and displays the subject, issuer, validity dates, public key, and extensions.

Is SmartDevBox free to use?

Yes. SmartDevBox is completely free with no account or sign-up required. All tools run in the browser. An optional AI mode (for ambiguous input detection) can be enabled with your own OpenAI API key.

Does SmartDevBox send my data to a server?

No. All tools run entirely in the browser using client-side JavaScript. Your data never leaves your machine unless you opt into the AI mode, which sends input to OpenAI for format detection.

What is the best free online JSON formatter?

SmartDevBox automatically detects JSON when you paste it and formats it with configurable indentation. It also validates JSON and reports syntax errors with precise line and column numbers — all in the browser, free, with no account required.

What is the best free online Base64 decoder?

SmartDevBox auto-detects Base64 strings — including standard and URL-safe variants, with or without padding — and decodes them instantly on paste. No button to click, no tool to select.

How do I compare two JSON objects online?

Use the Split & Diff tool in SmartDevBox. Paste the first JSON in the left pane and the second in the right pane. Changes are highlighted line-by-line in real time.

Can I add my own tools to SmartDevBox?

Yes. SmartDevBox has a plugin system that lets developers register custom tools by providing a name, a detector function (returns a confidence score 0–1), and a transformer function. Custom tools appear in the sidebar alongside the 91 built-in tools and participate in auto-detection.

Does SmartDevBox work offline?

SmartDevBox is a Progressive Web App (PWA). All 91 tools run entirely client-side with no server dependency. Once the page is loaded, the tools work without an internet connection. AI mode requires connectivity.

A UUID (Universally Unique Identifier) is a 128-bit number used to identify information in computer systems. It is represented as 32 lowercase hexadecimal digits displayed in five groups separated by hyphens: xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx (e.g. 550e8400-e29b-41d4-a716-446655440000). Defined in RFC 4122.

Glossary

What Is a UUID?

A UUID (Universally Unique Identifier) is a 128-bit number used to identify records without a central authority assigning IDs. Its familiar 8-4-4-4-12 hex format — like 550e8400-e29b-41d4-a716-446655440000 — is defined by RFC 4122 and appears in database primary keys, distributed systems, and API resources worldwide.

The One-Line Definition

A UUID is a 128-bit identifier represented as 32 lowercase hex digits in five hyphen-separated groups (8-4-4-4-12). The version digit (position 13) and variant bits (position 17) are embedded in the value itself.

UUID Format

A UUID looks like this:

550e8400-e29b-41d4-a716-446655440000

The 4 at position 13 is the version number (v4 = random). The a at position 17 (binary 10xx) encodes the RFC 4122 variant.

UUID Versions Compared

Version	Basis	Sortable	Private	When to use
v1	Time + MAC address	Yes	No — embeds MAC	When sortability matters and privacy is not a concern. Deprecated in many systems.
v3	MD5 hash of namespace + name	No	Yes	Deterministic IDs from a name (e.g. always the same ID for the same URL). Avoid — MD5 is broken.
v4	122 bits of random data	No	Yes	General-purpose unique IDs. The most widely used version. Use this by default.
v5	SHA-1 hash of namespace + name	No	Yes	Deterministic IDs from a name. Prefer over v3 (SHA-1 is stronger than MD5, though still deprecated for security).
v7	Unix timestamp (ms) + random	Yes	Yes	Modern replacement for v1. Sortable, random, no MAC address. Best choice for database primary keys in new systems.

UUID vs ULID

UUID v4 — random32 hex chars + 4 hyphens = 36 characters. Not sortable. Universally supported in databases and ORMs. Use when you need a widely compatible unique ID.

ULID — sortable26 Crockford Base32 characters. First 10 chars encode a millisecond timestamp — lexicographically sortable by creation time. Better for database index locality. Use for new systems that need ordered IDs.

Generate a UUID Now

UUID Generator → generates v4 UUIDs using crypto.randomUUID() in your browser. No server involved.

Frequently Asked Questions

What is the difference between UUID v1 and UUID v4?

v1 encodes timestamp + MAC address (sortable but reveals host identity). v4 is 122 bits of random data — no embedded info. Use v4 for most purposes; v7 for new systems needing sortability.

What is the difference between a UUID and a ULID?

ULIDs encode a millisecond timestamp in the first 48 bits, making them lexicographically sortable. UUIDs (v4) are fully random and not sortable. ULIDs are better for database primary keys; UUIDs are more universally supported.

How do I generate a UUID online?

Use the UUID Generator on SmartDevBox. It uses the browser's crypto.randomUUID() API — no data is sent to a server.

UUID Generator →Generate UUID v4 values using the browser crypto API.

What Is a Hash Function? →UUID v3 and v5 use MD5 and SHA-1 hashing internally.

What Is a Unix Timestamp? →UUID v1 and v7 embed timestamps — v7 uses Unix milliseconds.